Agentzon vs Shopify API + MCP

Agentzon

Public OpenAPI 3.1 description and llms.txt, with a whole-basket checkout that needs no account or key. The buyer pays on a private page, so a person completes each purchase. No status page, security.txt or registered seller address was found on agentzon.co, and 34 of 500 listed items cannot be bought.

Shopify API + MCP

Typed GraphQL schemas with quarterly versions supported at least 12 months. Closed platform. You can't self-host or change checkout internals.

Agentzon

1. Search with GET /api/products. Use only items with checkoutAvailable true and a non-null unitAmount, because a null price means unavailable, never free
2. Send every item and quantity in one POST /api/checkout, with a new Idempotency-Key for each purchase attempt and the same key only to retry that basket
3. Show the buyer the product image from /api/products/{id}/image and get their approval before opening the checkout URL
4. Tell the buyer that catalogue prices exclude sales tax, that shipping is U.S. only and that change-of-mind returns exclude hygiene and food items
5. Keep the checkout URL and the orderToken private. A paid status confirms payment, not shipment

Shopify API + MCP

1. Pin an API version in the URL and plan to move at least once a year. Old versions fall forward to the oldest supported one
2. Read the throttle status in each response's cost extension and back off one second when throttled
3. Send an agent profile in meta on every UCP call, and an idempotency key on every checkout write
4. Check userErrors on every mutation. A 200 response can still carry a failed write
5. Add @shopify/dev-mcp while writing code so the agent checks queries against the current schema